It sounds like you have a very lenient building inspector.
I am seat-of-the-pants engineering, I generally overbuild for joinery decisions, as well as my own personal taste. However, a very large portion of those responding to these forums Do use tables, modeling, and what not to arrive at sizing.
What type of roof are you buildig? You mention a ridge, and imply common purlins. Is there a truss involved? Principle Rafters? And how did you arrive at your "Fake Plate" design, as opposed to, say, Brackets, or some other system to allow flying rafters?
The more details you are able to provide, the more likely someone will be able to lead you to the answers you seek.
Also. It has never been terribly expensive for me to have my drawings reviewed, and stamped. I wouldn't rule out that option, even as you seek to satisfy the requirements yourself
